Power-conversion efficiencies (PCEs) higher than 19% have been realized from single-junction organic photovoltaics. [4][5][6][7][8] Moreover, ongoing studies on morphology control, energy loss, photophysical analysis, and photon utilization improve our understanding of the photoelectric conversion processes and motivate the development of OSCs. [9][10][11][12][13][14][15][16][17][18] Fundamental intermolecular interactions are widely known, important, and ubiquitous; however, their complicated impact on organic photovoltaics have not been comprehensively researched.Intermolecular interactions, including those between like and unlike molecules, are prevalent in OSCs. Apart from interactions between different layers, [19] intermolecular interactions play complicated roles in heterojunction active layers, owing to multiple-component mixed systems involving thermodynamics and kinetics procedures. [20] Brédas et al. illustrated the detailed relationship between donor/acceptor (D/A) interactions and polarizability, the charge-transfer state, and charge-separated state in fullerene solar cells, thereby highlighting the significance of interactions from the perspective of theoretical simulations. [21] Hou et al. controlled D/A interactions using halogenated end-caps of acceptors and Research on organic solar cells (OSCs) has progressed through material innovation and device engineering. However, well-known and ubiquitous intermolecular interactions, and particularly their synergistic effects, have received little attention. Herein, the complicated relationship between photovoltaic conversion and multidimensional intermolecular interactions in the active layers is investigated. These interactions are dually regulated by side-chain isomerization and end-cap engineering of the acceptors. The phenylalkyl featured acceptors (LA-series) exhibit stronger crystallinity with preferential face-on interactions relative to the alkylphenyl attached isomers (ITIC-series). In addition, the PM6 and LA-series acceptors exhibit moderate donor/acceptor interactions compared to those of the strongly interacting PM6/ITIC-series pairs, which helps to enhance phase separation and charge transport. Consequently, the output efficiencies of all LA series acceptors are over 14%. Moreover, LA-series acceptors show appropriate compatibility, host/guest interactions, and crystallinity relationships with BTP-eC9, thereby leading to uniform and well-organized "alloy-like" mixed phases. In particular, the highly crystalline LA23 further optimizes multiple interactions and ternary microstructures, which results in a high efficiency of 19.12%. Thus, these results highlight the importance of multidimensional intermolecular interactions in the photovoltaic performance of OSCs.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202208986.
